Display screen or portion thereof with a graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with agraphical user interface, showing our new design, according to a firstembodiment thereof; and,

FIG. 2 is a front view of a display screen or portion thereof with agraphical user interface, showing our new design, according to a secondembodiment thereof.

The broken line showing of a display screen with a graphical userinterface is included for the purpose of showing portions of the articlewhich form no part of the claimed design.

CLAIM The ornamental design for a display screen or portion thereof witha graphical user interface, as shown and described.